docs: def _parse_tag(self, el):
          """Extract the namespace and tag from an element."""
          ns = None
          tag = el.tag
          if tag[0] == '{':
              ns, tag = tag[1:].split('}', 1)
              if self.ns_map and ns in self.ns_map:
                  ns = self.ns_map[ns]
          return ns, tag